Summary of Stratigraphy

[Note: The geologic classification and nomenclature of this report follow the usage of the State Geological Survev of Kansas (Moore, and others, 1951 ) and do not conform in all respects to the usage of the U. S. Geological Survey.]

The geologic formations that crop out in Jackson County are of sedimentary origin and range in age from Pennsylvanian to Quaternary (Table 3). The areal distribution of the formations is shown on Plate 1. The Cedar Vale shale, which is Pennsylvanian in age, is the oldest formation exposed in the county. The Wreford limestone crops out in a small area along the extreme western edge of the county and is the youngest outcropping Paleozoic formation in the county. Much of the Paleozoic bedrock is mantled by deposits of Pleistocene glacial drift and Recent alluvium.

The character and ground-water supplies of the geologic formations are discussed in the section on geologic formations and their water-bearing characteristics.

Table 3--Generalized section of the geologic formations of Jackson Coitnty, Kansas. Classification of the State Geological Survey of Kansas [1953].

System

Series

Group

Formation

Members

Thickness, feet

Physical character

Water supply

Quaternary

Pleistocene

Alluvium

0-50

Silt and clay, with minor quantities of sand in the
upper part. Sand and gravel with thin beds of clay in the lower part.

Yields large quantities of water to wells along the
major streams of the county. Alluvium of minor tributary streams yields
supplies adequate for domestic or stock needs.

Sanborn formation

Peoria silt

0-3

Tan, massive silt.

Does not furnish water to wells in Jackson County.

Kansas till and associated deposits.

0-150

Unconsolidated clay and boulders, with incorporated
deposits of sand and gravel

Supplies small to moderate quantities of water to
many domestic and stock wells where a sufficient thickness lies below the
water table.

Atchison formation

0-110

Silt and very fine sand in the upper part, coarse
sand and fine gravel in the lower part.

Yields moderate supplies of water to wells in
eastern and northern Jackson County.

Pre-Kansan gravel

0-12

Medium to coarse chert gravel with a minor amount of
quartzite gravel.

Yields moderate supplies of water to a few wells in
the county.

Permian

Wolfcampian

Chase

Wreford limestone

Threemile limestone.

0-5

Cherty limestone beds, with thin beds of shale.

Not known to yield water to wells in Jackson County
due to its unfavorable topographic position.

Council Grove

Speiser shale

15-18

Varicolored shale and a thin but peristent limestone
bed.

Yields no water to wells in Jackson County.

Funston limestone

4-7

Massive gray limestone, and light colored shale.

Yields very little water to wells in Jackson County.

Blue Rapids shale

22?

Blocky gray shale, contains some green, red, and
black.

Yields no water to wells in Jackson County.

Crouse limestone

3-5

Massive and platy limestone, contains some shale.

Yields small quantities of water to a few wells.

Easly Creek shale

15-20

Light colored and red shale.

Yields no water to wells in Jackson County.

Bader limestone

Middleburg limestoneHooser shaleEiss limestone

13-18

Massive limestone beds, alternating with shale.

Yields small quantities of water to wells.

Stearns shale

20

Gray or green calcareous shale.

Yields no water to wells in Jackson County.

Beattie limestone

Morrill limestoneFlorena shaleCottonwood limestone

15-19

Gray to black shale and impure limestone in the
upper part, massive limestone in the lower part.

Geologic History

Paleozoic Era

The Paleozoic geologic history of the area is known because of the studies that have been reported in several publications. Lee (1943) shows that the area was subjected both to erosion and deposition during the Paleozoic Era. Jackson County is on the east flank of the Nemaha anticline and in the west part of the Forest City basin. Both of these structural features were developed mainly after Mississippian time. Logs of several oil-test wells in the county indicate that as much as 3,300 feet of sediment overlies Pre-Cambrian granite. All the Paleozoic systems are represented in either the subsurface or on the surface. Geologic conditions along the northern side of the county are shown in cross section by Jewett and Abernathy (1945, pl. 1), and along the eastern side of the county by Jewett (1949, pl. 2).

Mesozoic Era

After the retreat of Permian seas, erosion was the predominant geologic process until Quaternary time. No rocks of Mesozoic age occur in Jackson County, but possibly Cretaceous rocks were deposited and later removed by erosion.

Cenozoic Era

During the Tertiary Period Jackson County was again an area of erosion. Any Cretaceous rocks that may have been deposited and many feet of older sediments were stripped away by erosion. Several small areas in the county are strewn with poorly sorted chert gravel resting on Permian or Pennsylvanian beds. These gravel deposits may be remnants of Tertiary stream deposits. At the beginning of the Quaternary Period, continental ice sheets advanced toward the central United States. The first Pleistocene ice sheet, the Nebraskan, probably did not extend into Jackson County. The only known glacial deposits of Nebraskan age in Kansas are found at a considerable distance to the north and east of Jackson County (Frye and Leonard, 1952). Gravel classified as pre-Kansan in this report may have been deposited as a result of Nebraskan glaciation, or it may have been deposited as earliest Kansan outwash and would be comparable to the basal part of the Atchison formation.

An east-trending low area in the bedrock surface of northern Jackson County is probably a post-Nebraskan pre-Kansan valley eroded in a position marginal to the Nebraskan ice front (Frye and Walters, 1950). Deposits, locally as much as 100 feet thick, consisting of sand and silt in the upper part and sand and gravel at the base fill the lower part of this area. These deposits are pro-Kansan outwash and have been named the Atchison formation from exposures in Atchison County. Glacial deposits overlying the Atchison formation in this area are lithologically similar to Kansan deposits overlying the remainder of the county and are judged as being of Kansan age. The Kansan glacier, which was the second and last to invade Kansas, extended approximately as far south as Kansas River and as far west as Big Blue River. The surface developed in Jackson County and surrounding areas after the close of the Permian Period was mantled by thick deposits of glacial drift. Immediately after the retreat of the ice sheet the area probably was relatively flat, but many of the filled valleys were reopened by streams carrying meltwater from the retreating glacier. The Grand Island sand and gravel member of the Meade formation was deposited along these streams and is of late Kansan age. Thin veneers of eolian silt or loess were deposited over the flat uplands during later Pleistocene time, but at no place in Jackson County are these deposits thick enough to be an important source of ground water, and therefore they are not shown on the geological map.

Since the close of the Kansan Stage, streams have eroded their valleys to their present levels and have deposited alluvium and terrace deposits along their courses.